Facile Dual-Protection Layer and Advanced Electrolyte Enhancing Performances of Cobalt-free/Nickel-rich Cathodes in Lithium-Ion Batteries

Despite cobalt (Co)-free/nickel (Ni)-rich layered oxides being considered as one of the promising cathode materials due to their high specific capacity, their highly reactive surface still hinders practical application. Herein, a polyimide/polyvinylpyrrolidone (PI/PVP, denoted as PP) coating layer is demonstrated as dual protection for the LiNi0.96Mg0.02Ti0.02O2 (NMT) cathode material to suppress surface contamination against moist air and to prevent unwanted interfacial side reactions during cycling. The PP-coated NMT (PP@NMT) preserves a relatively clean surface with the bare generation of lithium residues, structural degradation, and gas evolution even after exposure to air with ∼30% humidity for 2 weeks compared to the bare NMT. In addition, the exposed PP@NMT significantly enhances the electrochemical performance of graphite||NMT cells by preventing byproducts and structural distortion. Moreover, the exposed PP@NMT achieves a high capacity retention of 86.7% after 500 cycles using an advanced localized high-concentration electrolyte. This work demonstrates promising protection of Co-free/Ni-rich layered cathodes for their practical usage even after exposure to moist air.